The demographic history of India: A perspective based on genetic evidence
Kuupäev
2010-08-19
Autorid
Ajakirja pealkiri
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Kirjastaja
Abstrakt
Soov mõista Lõuna-Aasia inimasustuse evolutsioonilist ajalugu on olnud juba kaua aega evolutsioonilise, populatsiooni- ja meditsiinigeneetika uurijate huviväljas. Siinses dissertatsioonis läbiviidud uurimistöö keskendus esmajoones makro-haplogrupp M uurimisele, mis moodustab 60% India rahvaste emaliinidest, samuti mõnede, fülogeneetiliselt informatiivsetele makro-haplogrupp R harudele. Meie eesmärgiks oli lokaliseerida haplogruppide ekspansiooni ajas ja ruumis ning testida mudeleid, mis kirjeldavad geenide ja kultuuride vahekorda ning hõimude ja kastide geneetilise varieeruvuse ruumi tervikuna. Analüüs tõi ilmseks mitmeid uusi sügavaid makro-haplogrupp M harusid, mis kinnitab seisukohta nende tekkest Lõuna-Aasias. Indo-euroopa keelt rääkiva Põhja-India mushari populatsiooni uurimine näitas, et nende geneetiline varieeruvus seletub kultuurilise nihkega, millega ei ole kaasnenud olulist geneetilist muutust. Me oletame, et tegemist on laialtlevinenud keelevahetuse fenomeniga. Meie uuringud teiste mtDNA haplogruppide, spetsiifiliselt R7 osas näitasid, et ürgsete emaliinide levikupilt seletub esmajoones subkontinendi geograafilise, mitte aga keelelise maastikuga. Kokkuvõttes me järeldame, et ulatuslik endogaamia, tingituna arvukatest kastide- ja hõimudesisestest ja -vahelistest sotsiaalsetest tõketest, võimendatuna lisaks erinevate evolutsiooniliste mõjurite poolt, nagu juhuslik geneetiline triiv, populatsioonide fragmenteerumine, kuid seda pikaajalise kõrge asustustiheduse foonil, on hoidnud India subkondinendi populatsioonid geneetiliselt mitmekesistena ja erinevatena. Rohkete autohtoonsete geeniliinide olemasolu Lõuna-Aasias näitab omakorda seda, et iseäranis sealsed emaliinide variatsioonid ei ole olulisel määral väljunud regioonist peale selle esmaasustamist ning mtDNA algse varieeruvuse teket. Saadud andmestik võimaldab kavandada mitmeid uusi uurimissuundi selleks, et kaevuda sügavamalt Lõuna-Aasia rahvaste geneetilisse pärandi kihtidesse.
An understanding of evolutionary history of peopling of South Asia has long been a subject of interest for the researchers working in evolutionary, population and medical genetics. The work undertaken in this thesis was largely focused on macrohaplogroup M encompassing 60% of Indian maternal genepool, and to some phylogeographically informative branches of macrohaplogroup R. Our aim was to localize likely haplogroup expansions in space and time(s) and to test further the gene-culture and caste-tribe genetic continuum models. Our analysis revealed several novel deep rooting lineages of macrohaplogroup M, reinforcing the concept of in-situ origin of these clades in South Asia. Our genetic analysis on Indo-European speaking Mushar population of North India reflected the cultural process in South Asia, where language shift has taken place by cultural diffusion, without any large genetic exchange. We assume that this is a widespread phenomenon, not restricted to South Asia. Our study on the origins of other mtDNA haplogroups, in particular haplogroup R7, indicates that the spread of South Asian specific ancient matrilineages follow predominantly geographic rather than linguistic landscape of the subcontinent. Overall, we conclude that high level of endogamy created by numerous social boundaries within and between castes and tribes, along with the influence of several evolutionary forces such as genetic drift, fragmentation, but in parallel long time large population size, has kept the Indian subcontinent populations genetically diverse and distant from each other. At the same time, presence of a large variety of autochthonous to South Asia genetic lineages suggests log-time limited gene flow between India and neighbouring it continental populations, in particular outflow of the Indian matrilineal pool after the settlement of the subcontinent and initial diversification of its mtDNA pool. The obtained results allow to formulate a number of new avenues of research to further explore the strata of genetic heritage of South Asia.
An understanding of evolutionary history of peopling of South Asia has long been a subject of interest for the researchers working in evolutionary, population and medical genetics. The work undertaken in this thesis was largely focused on macrohaplogroup M encompassing 60% of Indian maternal genepool, and to some phylogeographically informative branches of macrohaplogroup R. Our aim was to localize likely haplogroup expansions in space and time(s) and to test further the gene-culture and caste-tribe genetic continuum models. Our analysis revealed several novel deep rooting lineages of macrohaplogroup M, reinforcing the concept of in-situ origin of these clades in South Asia. Our genetic analysis on Indo-European speaking Mushar population of North India reflected the cultural process in South Asia, where language shift has taken place by cultural diffusion, without any large genetic exchange. We assume that this is a widespread phenomenon, not restricted to South Asia. Our study on the origins of other mtDNA haplogroups, in particular haplogroup R7, indicates that the spread of South Asian specific ancient matrilineages follow predominantly geographic rather than linguistic landscape of the subcontinent. Overall, we conclude that high level of endogamy created by numerous social boundaries within and between castes and tribes, along with the influence of several evolutionary forces such as genetic drift, fragmentation, but in parallel long time large population size, has kept the Indian subcontinent populations genetically diverse and distant from each other. At the same time, presence of a large variety of autochthonous to South Asia genetic lineages suggests log-time limited gene flow between India and neighbouring it continental populations, in particular outflow of the Indian matrilineal pool after the settlement of the subcontinent and initial diversification of its mtDNA pool. The obtained results allow to formulate a number of new avenues of research to further explore the strata of genetic heritage of South Asia.
Kirjeldus
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Märksõnad
doktoritööd, bioloogia, India, geneetika, demograafia